Someone has stolen a valuable formula from Sir Claud Amory, Britian’s leading physicist (Bud Emerson).  As he announces the theft at a dinner party;  Sir Claud outlines the suspects:  his son, Richard (Steve Murdock), Richard’s wife Lucia (Elizabeth Mander-Wilson), his sister Caroline (Lizette Kent Allen), his niece Barbara (Jessica Seaman), his secretary Edward Raynor (Terence J. Burke), and Dr. Carelli (Nicolas Peters), an unexpected Italian guest who has stopped to visit Lucia.  Sir Claud has already asked for help in retrieving the formula from Hercule Poirot (Michael Gardner) who shows up as scheduled ready to solve the mystery with help from his friend Captain Hastings (Ivan Harrison).   Rounding out the cast are the butler Tredwell (Timothy Paul Evans), Inspector Japp (Nick Reeves), and Dr. Graham (Eric Hedberg).